The invention relates to a keyboard comprising a plurality of guidance components in each of which a key is movably mounted, with the guidance components being segments of an integral multiple key-guiding arrangement with a gummous mat that forms domes, e.g. for resetting pressed keys, and with a contact level which carries conductor tracks and contact arrangements, each switchable by one particular key.
Keyboards of this kind are known. They are characterized by having functional elements required for a single key position--multiplied in the form of levels, or layers--being available for several or all key positions. Such levels are easy to handle and eventually lead to inexpensive keyboards. Design and arrangement of the individual keyboard levels can vary. It is known, for instance, to further equip the domes of the gummous mat with electrically conductive surfaces for switching purposes (EP-A-0 453 274). The contact level can consist of a foil covered with electrically conductive surfaces, with a carrier level for mechanical stabilization located under the foil, if necessary. Printed boards with etched-out conductive surfaces, for example, are also known for use as contact levels (EP-A-0 3.98 186). Document EP-A-0 305 931 shows a multiple key-guiding arrangement with an integral keyboard casing. Genuine foil keyboards consist of a contact level and a closed keying level; operating keys and the necessary guidance and resetting elements are not part of foil keyboards.
In the case of the kind of keyboards described in the introductory paragraph, a number and distribution of the positions of the keys are determined by a tool used in manufacturing. This is true in particular with regard to the complex design of a multiple key guidance system. Dimensional changes in a field of keys, resulting from key positions, which in their entirety are desired after completion, require major work efforts and can sometimes only be carried out efficiently by using a new tool. In small-batch production both possibilities are inefficient.
Solutions are known which allow for any modification desired or for a limited modification of a field of keys. In EP-A-0 094 839, for example, there is a suggestion to create a desired field of keys by arranging individual key-guiding arrangements or small groups of key-guiding arrangements next to each other on any side. The key-guiding strips known from EP-A-0 087 369 and the strip-type tongues of the readjusting springs allow for a line-by-line extension of the field of keys. Such individual or grouped operational elements of a keyboard are difficult to handle.